Method for stainproofing treatment and product having glass layer, reinforced pottery and method for production thereof, and product having glass layer and method for production thereof

ABSTRACT

A product having a glass layer is produced that can be produced at low cost and can exhibit excellent antibacterial function. A base body, a first glazing material capable of forming a first glass layer on a surface of the base body, and a second glazing material capable of forming a second glass layer containing a silver compound on the surface of the base body. A first glazing material layer comprising the first glazing material and, on the surface side, a second glazing material layer comprising the second glazing material are formed on the surface of the base body. The first glazing material layer and the second glazing material layer are melted to form a first glass layer and a second glass layer. The second glazing material layer has a higher viscosity upon melting than the first glazing material layer.

TECHNICAL FIELD

The first invention relates to a process for stain resistant treatmentand a product having a glass layer. The second invention relates to areinforced ceramic product and a process for producing the same. Thethird invention relates to a product having a glass layer and a processfor producing the same.

BACKGROUND ART

It has been known that antibacterial metals, for example, Ag, Cu, Zn andthe like, have an antibacterial activity. Therefore, in the case where aproduct having a glass layer, such as a ceramic product, an enameledproduct and the like, having an antibacterial activity is to beproduced, a process for stain resistant treatment is carried out, whichhas an antibacterial treatment step of imparting antibacterial functionto a surface of a base body, such as a glass molded article, a ceramicmolded article, a metallic molded article and the like. Theantibacterial treatment step of the process for stain resistanttreatment contains a preparation step of preparing a glazing materialcapable of forming a glass layer containing an antibacterial metal, anda vitrification step of forming a glazing material layer formed with theglazing material on the surface of the base body and melting the glazingmaterial layer to form a glass layer.

According to the process for stain resistant treatment, a product isobtained that comprises a base body having a glass layer, and the glasslayer comprises the glazing material. In the product having a glasslayer thus obtained, the antibacterial metal in the glass layer canaffect bacteria to kill them or to suppress propagation thereof.

An ordinary ceramic product comprises a ceramic main body and a glasslayer formed on the surface of the ceramic main body.

The ceramic product is produced roughly in the following manner. As apreparation step, a base material that can form a ceramic main body anda glazing material that can form a glass layer on the surface of theceramic main body are prepared. As a glazing step, a glazing materiallayer comprising the glazing material is formed on the surface of thebase material. Thereafter, as a baking step, the base material and theglazing material layer are baked to obtain a ceramic product comprisingthe ceramic main body and the glass layer.

In the ceramic product thus obtained, the glass layer finishes thesurface being smooth and fine, and makes the surface being difficult tobe damaged and having water-proofing property.

Furthermore, ceramic materials used as products, such as table wares,kitchen equipments, ornamental articles, tiles, sanitary goods, electricequipments, physical and chemical equipments, industrial equipments,roof tiles, ceramic pipes and the like, comprise a ceramic main body asa base body and a glass layer formed on the surface of the ceramic mainbody. Enameled product comprises a metallic main body as a base body anda glass layer formed on the surface of the metallic main body. Further,part of glass products comprises a glass main body as a base body and aglass layer formed on the glass main body.

Among the foregoing products having a glass layer, a ceramic material,for example, is produced roughly in the following manner. As apreparation step, a base material that can form a ceramic main body anda glazing material that can form a glass layer on the surface of theceramic main body are prepared. As a glazing step, a glazing materiallayer comprising the glazing material is formed on the surface of thebase material. Thereafter, as a baking step, the base material and theglazing material layer are baked to obtain a ceramic product comprisingthe ceramic main body and the glass layer. In the product, the glasslayer is finished to have a surface being smooth and fine, the surfaceis difficult to suffer formation of flaws, and water-proofing propertyis imparted.

DISCLOSURE OF THE INVENTION

(First Invention)

However, because a single glass layer is only formed on the surface ofthe base body in the ordinary process for stain resistant treatment,exertion of the antibacterial function to bacteria on the surface of theglass layer is naturally expected, but the antibacterial metal isdispersed in the glass layer. Therefore, in a product having the glasslayer thus obtained, the effect thereof is low unless the concentrationof the antibacterial metal is increased. Accordingly, in the process forstain resistant treatment, a large amount of the antibacterial metal isconsumed to exhibit the excellent antibacterial function to causeincrease of the production cost.

The first invention has been developed under the circumstances of theconventional art, and an object to be attained thereby is to produce aproduct having a glass layer that can be produced at a low cost and canexhibit excellent antibacterial function.

The process for stain resistant treatment of the first invention is aprocess for stain resistant treatment comprising an antibacterialtreatment step of imparting antibacterial function to a surface of abase body,

-   -   characterized in that the antibacterial treatment step comprises        a preparation step of preparing the base body, a first glazing        material capable of forming a first glass layer on a surface of        the base body, and a second glazing material capable of forming        a second glass layer containing an antibacterial metal on the        surface of the base body, and    -   a vitrification step of forming a first glazing material layer        comprising the first glazing material on a surface of the base        body and, on a yet surface side, a second glazing material layer        comprising the second glazing material, and melting the first        glazing material layer and the second glazing material layer to        form the first glass layer and the second glass layer, and    -   the second glazing material layer has a higher viscosity upon        melting than the first glazing material layer.

In the process for stain resistant treatment of the first invention, asa preparation step of an antibacterial treatment step, a base body, afirst glazing material capable of forming a first glass layer on asurface of the base body and a second glazing material capable offorming a second glass layer containing an antibacterial metal on thesurface of the base body are prepared. As a vitrification step of anantibacterial treatment step, a first glazing material layer comprisingthe first glazing material on a surface of the base body and, on a yetsurface side, a second glazing material layer comprising the secondglazing material are formed on a surface of the base body, and the firstglazing material layer and the second glazing material layer are meltedto form the first glass layer and the second glass layer.

Herein, because the viscosity upon melting of the second glazingmaterial layer is higher than the first glazing material layer, theantibacterial metal is difficult to be diffused from the second glasslayer on the surface side into the first glass layer, and almost allthereof stays in the second glass layer. Therefore, in the process forstain resistant treatment, even when a large amount of an antibacterialmetal is not consumed, the antibacterial metal in the second glass layeraffects bacteria as naturally expected, so as to exhibit excellentantibacterial function.

Furthermore, in the process for stain resistant treatment of the firstinvention, the first glazing material layer comprising the first glazingmaterial and, on a yet surface side, the second glazing material layercomprising the second glazing material layer are formed, and the firstglazing material layer and the second glazing material layer are meltedto form the first glass layer and the second glass layer, and thus inthe resulting product, the second glazing material is impregnated intothe first glazing material layer, whereby the first glass layer and thesecond glass layer are firmly adhered, and formation of cracks growingat an interface between them can be prevented. Furthermore, according tothe procedure, the baking step can be completed all at once to realizereduction in production cost.

Therefore, according to the process for stain resistant treatment,production can be carried out at a low cost, and a product having aglass layer that can exhibit excellent antibacterial function can beproduced.

The product having a glass layer of the first invention is thus obtainedin the foregoing manner. The product having a glass layer of the firstinvention comprises a base body having a glass layer, and the glasslayer comprises a first glass layer comprising a first glazing materialand a second glass layer formed on a yet outer side of the first glasslayer and comprising a second glazing material containing anantibacterial metal and being different from the first glazing material.

As for the base body, in the case where a glass product is produced asthe product having a glass layer, the glass molded article can beemployed; in the case where a ceramic material, such as sanitary ceramicwares, tiles and the like, is produced, the ceramic molded article canbe employed; and in the case where an enameled product is produced, themetallic molded article can be employed.

As the antibacterial metal contained in the second glazing material, Ag,Cu, Zn and the like can be employed. Specific examples include anorganic silver or copper compound and a silver or copper carryinginorganic compound, and (1) silver, copper and a silver-copper alloy;(2) silver phosphate, silver nitrate, silver chloride, silver sulfide,silver oxide, silver sulfate, silver citrate and silver lactate; (3)cuprous phosphate, cupric phosphate, an organic copper compound, cuprouschloride, cupric chloride, cuprous sulfide, cuprous oxide, cupric oxide,cupric sulfide, cuprous sulfate, cupric sulfate, copper citrate andcopper lactate; and the like. As for zinc, an organic zinc compound anda zinc carrying inorganic compound are similarly exemplified, and zinc,zinc oxide, zinc chloride, zinc sulfide, zinc sulfate, zinc lactate andthe like can be employed. These antibacterial metals may be an elementalsubstance or an alloy, and also may be a compound.

In the product having a glass layer of the first invention, the firstglass layer and the second glass layer preferably have a difference inthickness of from 10/1 to 30/1. According to the configuration, even inthe case where the appearance of the second glass layer is poor due tothe inclusion of the antibacterial metal, such as Ag and the like, inthe second glass layer, for example, such a surface is obtained that hassubstantially no difference on appearance from the case where only thefirst glass layer is formed, and a product having an appearance of thesurface that is excellent in design can be obtained.

According to the results of experiment by the inventors, in the producthaving a glass layer of the first invention, the second glass layer alarger amount of potassium and a smaller amount of sodium than the firstglass layer. Potassium has a larger ionic radius than sodium. Therefore,it is considered that upon forming the glass layer of the product of thefirst invention, sodium ions in the second glass layer are ion-exchangedby potassium ions in the first glass layer to cause a compression stressin the second glass layer, whereby the strength of the second glasslayer is increased.

Furthermore, in the process for stain resistant treatment of the firstinvention, it is preferred that the second glazing material contains aphosphoric acid compound. In the product having a glass layer of thefirst invention thus obtained, a phosphoric acid compound, such as P₂O₅and the like, is present in the second glass layer, and thus theantibacterial function owing to the antibacterial metal is more liableto be exhibited. It is also preferred that a boric acid compound iscontained in the second glazing material. According to theconfiguration, a boric acid compound, such as B₂O₃ and the like, ispresent in the second glass layer, and thus the antibacterial functionowing to the antibacterial metal is more liable to be exhibited.

The process for stain resistant treatment of the first inventionpreferably comprises a water repellent treatment step of subjecting thesurface of the second glass layer to a water-repellent treatment.According to the configuration, both the antibacterial function and thewater repellent function are imparted to the surface of the second glasslayer, and thus in the case where water containing a large amount ofstain components, to which the stain resistant effect is insufficientonly by the antibacterial function, is applied, the stain is difficultto remain owing to the water repellent function, whereby the stainresistant effect is sufficiently exerted.

In this case, the water repellent treatment step can be carried out byforming a film comprising a water repellent treatment liquid havingsilicon-containing functional groups that are bonded to hydroxyl groupspresent on the surface of the second glass layer through a dehydrationreaction or a dehydrogenation reaction. When the treatment is carriedout, the silicon-containing functional groups are bonded to the hydroxylgroups (—OH) present on the surface of the second glass layer through adehydration reaction or a dehydrogenation reaction to shield thehydroxyl groups. Therefore, when water containing a large amount of ametallic ion, such as soluble silica and the like, is used, the hydroxylgroups are inactivated and are not bonded to the metallic ion, and thusthey are not bonded to such a component as human excrement. Inparticular, when water containing soluble silica as the metallic ion isused, it is not deposited or difficult to be deposited as silicic acidforming a network structure, and thus stain is difficult to beincorporated. Therefore, when the water repellent treatment liquidcontains the silicon-containing functional groups, stain, such as humanexcrement and the like, is difficult to be adhered to a product usedsimultaneously with water containing a large amount of a metallic ion,such as soluble silica, and cleaning thereof is easily carried out.

Herein, the water repellent treatment liquid is preferably one having nosilicon-containing functional groups bonded to each other. According tothe configuration, as the results of experiment by the inventors, stainresistant effects for water scale stain resistance, hairdye stainresistance, wear resistance and alkali resistance are improved. When thesilicon-containing groups of the water repellent treatment liquid arebonded to each other, the amount of silicon is increased to depositsilicic acid forming a network structure in the film, and stain isliable to be incorporated therein.

The water repellent treatment liquid preferably has carbon fluoridegroup at the ends bonded to the silicon-containing functional groups. Asthe results of experiment by the inventors, when the carbon fluoridegroups are incorporated in this manner, the water repellent function issuccessfully exerted by the small critical surface tension of the carbonfluoride groups, large effects are obtained for water scale stainresistance, hair dye stain resistance and alkali resistance.

Herein, the carbon fluoride group may be —C_(n)F_(2n+1) (n is a naturalnumber of 1≦n≦12). As the results of experiment by the inventors,according to the configuration, because the number of fluorine becomeslarge, and fluorosilane is bulky, large effects are obtained for waterscale stain resistance, hairdye stain resistance, wear resistance andalkali resistance.

The water repellent treatment liquid may be one formed by mixing a firstagent and a second agent, in which the first agent is a co-hydrolysisproduct of a perfluoroalkyl group-containing organic silicon compoundand a hydrolyzable group-containing methylpolysiloxane compound in ahydrophilic solvent, and the second agent is a mixture of anorganopolysiloxane and a strong acid. Herein, the perfluoroalkylgroup-containing organic silicon compound and the hydrolyzablegroup-containing methylpolysiloxane compound present in the first agentare bonded to the hydroxyl groups present on the surface of the glasslayer through a dehydration reaction or a dehydrogenation reaction, soas to be prepared as a component having silicon-containing functionalgroups for protecting the hydroxyl groups.

The reason why the perfluoroalkyl group-containing organic siliconcompound is used as a constitutional component of the first agent is thea large stain resistant effect is also exhibited as a water repellentfunction owing to the large critical surface tension of the carbonfluoride groups, so as to provide large effects for water scale stainresistance, hairdye stain resistance and alkali resistance. The reasonwhy the hydrolyzable group-containing methylpolysiloxane compound isused as a constitutional component of the first agent is that largeeffects are obtained for water scale stain resistance, hairdye stainresistance and alkali resistance.

The second agent is a mixture of an organopolysiloxane and a strongacid. The reason why the organopolysiloxane is used as a constitutionalcomponent of the second agent is that stain resistant effects areexerted a slip stick stain resistance and wear resistance owing to thesmall critical surface tension of alkyl groups. The reason why thestrong acid is used as a constitutional component of the second agent isthat in the case where the stain resistant treatment is carried out byusing the water repellent treatment liquid prepared in the mannerrelating to the first invention, the strong acid effectively acts as acatalyst for bonding the perfluoroalkyl group-containing organic siliconcompound and the hydrolyzable group-containing methylpolysiloxanecompound as constitutional components in the first agent with thehydroxyl groups on the surface of the glass layer.

When the first agent and the second agent are mixed, it is consideredthat silanol groups of the co-hydrolysis product react with theorganopolysiloxane and the strong acid to form siloxane bonds (Si—O—Si)through a dehydration reaction, so as to form an addition compound ofplural molecules intertangled by each other in a complex manner.Therefore, it is considered that the water repellent treatment liquidformed by mixing the first agent and the second agent is not formed fromsingle molecules of the perfluoroalkyl group-containing organic siliconcompound, the hydrolyzable group-containing methylpolysiloxane compound,the organopolysiloxane and the like, but is constituted by the additioncompound formed by intertangling these molecules in a complex manner,i.e., a kind of polymer, and also the addition compound and the surfaceof the base body are firmly bound by a chemical bond.

According to the manner, a product having a glass layer of the firstinvention having a water repellent layer containing a water repellentcomponent on the surface side of the second glass layer. Because thethickness of the water repellent layer is extremely small, and the waterrepellent layer is bonded only on the hydroxyl group part of the surfaceof the second glass layer, it is considered that the antibacterialeffect penetrates the drain layer.

(Second Invention)

The conventional ceramic product is liable to suffer formation of flawson the surface thereof, and the surface hardness thereof is insufficientbecause it has a single glass layer. Therefore, it has such adisadvantage that cracks are liable to occur in the glass layer or thelike upon receiving an impact due to the presence of flaws.Particularly, in the case of a ceramic product imparted with anantibacterial function on the surface by impregnating the glass layerwith an antibacterial metal, such as Ag and the like, the tendency isexpected to be large because it is considered that the antibacterialmetal accelerates the growth of cracks. It also has such a disadvantagethat stain is liable to be attached to the flaws.

The second invention has been developed under the circumstances of theconventional art, and an object to be attained thereby is to provide areinforced ceramic product that is difficult to suffer formation offlaws on the surface thereof.

The reinforced ceramic product of the second invention comprises aceramic product main body and a glass layer formed on a surface of theceramic product main body, characterized in that the glass layercomprises a first glass layer comprising a first glazing material and asecond glass layer comprising a second glazing material that is formedon an outer side of the first glass layer and has a smaller linearthermal expansion coefficient than the first glass layer.

In the reinforced ceramic product of the second invention, because thelinear thermal expansion coefficient of the second glass layer issmaller than the linear thermal expansion coefficient of the first glasslayer, the second glass layer suffers compression stress due tocontraction of the first glass layer through the melting process of thefirst and second glazing material layers and the cooling process of thefirst and second glass layers in the baking step. Therefore, the secondglass layer is compacted to have a high surface hardness and isdifficult to suffer formation of flaws on the surface of the glasslayer. Therefore, in the reinforced ceramic product of the secondinvention, cracks in the glass layer or the like due to the flaws aredifficult to be formed. Attachment of stain due to the flaws is alsodifficult to occur, because the flaws are difficult to be formed.

The reinforced ceramic product of the second invention may have three ormore glass layers on the ceramic product main body. For example, in thecase where it has three glass layers, the lowermost layer corresponds tothe first glass layer, the intermediate layer corresponds to the secondglass layer and simultaneously corresponds to the first glass layer withrespect to the upper layer, and the upper layer corresponds to thesecond glass layer.

In the reinforced ceramic product of the second invention, it ispreferred that the ceramic product main body has a larger linear thermalexpansion coefficient than the first glass layer. According to theconfiguration, not only the second glass layer receives compressionstress from the first glass layer, but also the first glass layerreceives compression stress from the ceramic product main body throughthe sintering process of the base material, the melting process of theglazing material layers and the cooling process of the ceramic productmain body and the glass layers in the baking step, whereby not only thesecond glass layer but the first glass layer are compacted. Therefore,in the reinforced ceramic product of the second invention, cracks in theglass layer or the like due to the flaws are difficult to be formed.

In the reinforced ceramic product of the second invention, it ispreferred that the first glass layer and the second glass layer have adifference in linear thermal expansion coefficient of from 1×10⁻⁷ to1×10⁻⁶/° C. In the case where the difference in thermal expansioncoefficient between the first glass layer and the second glass layer issmaller than the range, a desired surface hardness cannot be obtained,and on the other hand, it is larger than the range, the compressionstress received by the second glass layer from the first glass layerbecomes too large to cause possibility of breakage of the second glasslayer. In particular, according to the results of experiment by theinventors, it is practical that the first glass layer and the secondglass layer have a difference in linear thermal expansion coefficient offrom 2×10⁻⁷ to 5×10⁻⁷/° C.

In this case, it is preferred that the first glass layer and the secondglass layer have a difference in thickness of from 10/1 to 30/1.According to the configuration, even in the case where the appearance ofthe second glass layer is poor due to the inclusion of the antibacterialmetal, such as Ag and the like, in the second glass layer, such asurface is obtained that has substantially no difference on appearancefrom the case where only the first glass layer is formed, and areinforced ceramic product having an appearance of the surface that isexcellent in design can be obtained.

Depending on the composition and the thickness of the second glasslayer, interference of light on the interface with the first glass layeris difficult to be formed, and thus iridescent can also be prevented.Further, depending on the composition of the second glass layer, thesecond glass layer is formed as a crystallized vitreous material to makeit opaque.

It is preferred that the ceramic product main body and the first glasslayer have a difference in linear thermal expansion coefficient of from1×10⁻⁷ to 1×10⁻⁶/° C. In the case where the difference in thermalexpansion coefficient between the ceramic product main body and thefirst glass layer is smaller than the range, a desired strength cannotbe obtained, and on the other hand, it is larger than the range, thecompression stress received by the first glass layer from the ceramicproduct main body becomes too large to cause possibility of breakage ofthe first glass layer. In particular, according to the results ofexperiment by the inventors, it is practical that the ceramic productmain body and the first glass layer have a difference in linear thermalexpansion coefficient of from 2×10⁻⁷ to 5×10⁻⁷/° C.

According to the results of experiment by the inventors, in thereinforced ceramic product of the second invention, the second glasslayer contains a larger amount of potassium and a smaller amount ofsodium than the first glass layer. Potassium has a larger ionic radiusthan sodium. Therefore, it is considered that upon forming the glasslayers of the ceramic product of the second invention, sodium ions inthe second glass layer are ion-exchanged by potassium ions in the firstglass layer to cause a compression stress in the second glass layer,whereby the strength of the second glass layer is increased.

In the case where an antibacterial metal is dispersed throughout asingle glass layer to impart antibacterial function to a ceramicproduct, the antibacterial metal is liable to sequester the vitreousmaterial, and thus cracks are liable to grow through the antibacterialmetal. Therefore, the reinforced ceramic product of the second inventionexhibit a larger effect when the second glass layer contains anantibacterial metal. According to the configuration, because the secondglass layer containing the antibacterial metal is compacted, growth ofcracks in the second glass layer through the antibacterial metal can beprevented. In the reinforced ceramic product of the second invention,since the antibacterial metal is contained only in the second glasslayer among the glass layers, the concentration of the antibacterialmetal on the surface side can be increased even when a smaller amount ofthe antibacterial metal than the conventional product is employed, whereby higher antibacterial function can be exerted. Further, unnecessaryconsumption of the antibacterial metal can be prevented.

As the antibacterial metal herein, those similar to the first inventioncan be employed.

Furthermore, in the reinforced ceramic product of the second invention,it is preferred that a water repellent layer containing a waterrepellent component is formed on the surface side of the second glasslayer. According to the configuration, even when water containing alarge amount of stain components is applied to the surface having aslight amount of flaws, the stain is difficult to remain owing to thewater repellent function to exhibit excellent stain resistant effect.

In this case, the same water repellent treatment step as in the firstinvention can be carried out.

The process for producing a reinforced ceramic product of the secondinvention comprises a preparation step of preparing a base materialcapable of forming a ceramic product main body and a glazing materialcapable of forming a glass layer on a surface of the ceramic productmain body, a glazing step of forming a glazing material layer comprisingthe glazing material on a surface of the base material, and a bakingstep of baking the base material and the glazing material layer toobtain a ceramic product comprising the ceramic product main body andthe glass layer, characterized in that the glazing material comprises afirst glazing material that is formed on a side of the base material andforms a first glass layer, and a second glazing material that is formedon an outer side and forms a second glass layer having a smaller linearthermal expansion coefficient than the first glass layer. The reinforcedceramic product of the second invention can be produced by theproduction process of the second invention.

In the process for producing a reinforced ceramic product of the secondinvention, it is possible in the glazing step that a first glazingmaterial layer comprising the first glazing material is formed, and thena second glazing material layer comprising the second glazing materialis formed on the first glazing material layer. In the reinforced ceramicproduct of the second invention thus obtained, the first glazingmaterial is impregnated into the surface side of the base material sincethe first glazing material is glazed on the base material to form afirst glazing material layer, and the first glazing material impregnatedinto the base material also forms the first glass layer inside theceramic product formed of the base material. Therefore, the first glasslayer is firmly adhered on the ceramic product main body. Further, inthe reinforced ceramic product, because the second glazing material isglazed on the first glazing material layer to form the second glazingmaterial layer, the second glazing material is impregnated into thefirst glazing material layer, whereby the first glass layer and thesecond glass layer are firmly adhered, and also the formation of cracksgrowing at the interface thereof can be prevented. According to theconfiguration, the baking step can be completed all at once, andreduction in production cost can be realized.

Furthermore, in the process for producing a reinforced ceramic materialof the second invention, it is preferred that the first glazing materialcontains potassium, and the second glazing material contains sodium.Because potassium has a larger ionic radius than sodium, sodium ions inthe second glazing material are ion-exchanged by potassium ions in thefirst glazing material by using these first and second glazingmaterials. Accordingly, a reinforced ceramic material of the secondinvention can be obtained that has the second glass layer containing alarger amount of potassium and a smaller amount of sodium than the firstglass layer.

In the process for producing a reinforced ceramic product of the secondinvention, it is possible that the second glazing material contains anantibacterial metal. According to the configuration, a reinforcedceramic product imparted with antibacterial function can be produced.

Furthermore, in the process for producing a reinforced ceramic productof the second invention, it is possible that the second glazing materialhas a higher viscosity upon melting than the first glazing material.According to the configuration, degasification upon baking is smoothlycarried out, whereby blister of the reinforced ceramic product can beprevented, and also the rate of diffusion of the antibacterial metalfrom the second glass layer to the first glass layer upon baking isdecreased, so as to produce a reinforced ceramic product having theconcentration of the antibacterial metal on the surface that ismaintained at a high level.

Furthermore, the process for producing a reinforced ceramic product ofthe second invention may have a water repellent treatment step ofsubjecting the surface of the glass layer to a water repellenttreatment. According to the configuration, such a reinforced ceramicproduct can be obtained that stain is difficult to remain.

(Third Invention)

A conventional product having a glass layer is liable to sufferformation of flaws on the surface thereof, and the surface hardnessthereof is insufficient because the glass layer is a single layer.Therefore, it has such a disadvantage that cracks are liable to occur inthe glass layer or the like upon receiving an impact due to the presenceof flaws. It also has such a disadvantage that stain is liable to beattached to the flaws. Therefore, it is considered to employ a glasslayers of plural layers. However, it has been found that a productsimply using a glass layer of plural layers is still liable to sufferformation of flaws, and the surface hardness thereof is insufficient.Accordingly, it has such a disadvantage that it lacks stain resistance.

The third invention has been developed under the circumstances of theconventional art, and an object to be attained thereby is to provide aproduct having a glass layer that is difficult to suffer formation offlaws on the surface thereof and thus certainly exerts excellent stainresistance.

The product having a glass layer of the third invention comprises a basebody and a glass layer formed on a surface of the base body,characterized in that the glass layer comprises a first glass layercomprising a first glazing material and a second glass layer comprisinga second glazing material that is formed on an outer side of the firstglass layer and has a smaller linear thermal expansion coefficient thanthe first glass layer, and hard fine particles are dispersed on asurface of the second glass layer.

In the product having a glass layer of the third invention, because thelinear thermal expansion coefficient of the second glass layer issmaller than the linear thermal expansion coefficient of the first glasslayer, the second glass layer suffers compression stress due tocontraction of the first glass layer through the melting process of thefirst and second glazing material layers and the cooling process of thefirst and second glass layers in the baking step. Therefore, the secondglass layer is compacted to have a high surface hardness and isdifficult to suffer formation of flaws on the surface of the glasslayer. Further, cracks in the glass layer or the like due to the flawsare difficult to be formed. Therefore, in the product of the thirdinvention, stain due to flaws and cracks is difficult to be attached,and excellent stain resistance can be exerted.

Particularly, in the case where the product of the third invention isexposed to external factors that damages the surface of the second glasslayer, the hard fine particles present on the surface prevent abrasionof the factors on the surface of the second glass layer. Therefore, evenwhen the factors abrade the surface of the second glass layer, theperiod of time thereof is short, and heavy flaws are difficult to beformed. Therefore, in the product of the third invention, stain isdifficult to be attached, and excellent stain resistance is exerted.

In the product of the third invention, because the linear thermalexpansion coefficient of the second glass layer is smaller than thelinear thermal expansion coefficient of the first glass layer, pinholesare difficult to be formed in the second glass layer. Therefore, theproduct has higher smoothness and realizes excellent stain resistance.

The product having a glass layer of the third invention may have a threeor more glass layers on the base body. For example, in the case where ithas three glass layers, the intermediate layer corresponds of the firstglass layer, and the upper layer corresponds to the second glass layer.

As the hard fine particles used in the product having a glass layer ofthe third invention, metallic fine particles and inorganic material fineparticles, such as silicon nitride fine particles and the like, can beemployed. The hard fine particles preferably have an average particlediameter of from 0.8 to 20 μm. According to the configuration, theforgoing flaw formation resistance is exhibited, and good appearance ofthe product having a glass layer can be maintained.

According to the results of experiment by the inventors, zircon fineparticles are preferably employed. Zircon fine particles have suchnature that is harder than the forgoing factors that form flaws on thesurface of the second glass layer. As such factors, a brash and anabrasive for cleansing is considered. The factors are scraped by thezircon fine particles, and thus the factors are difficult to form flawson the second glass layer.

The zircon fine particles exert flaw formation resistance as describedin the foregoing, but on the other hand, they impair smoothness of thesurface of the second glass layer and influence coloration of the secondglass layer, depending on the proportion contained in the second glasslayer. Therefore, the proportion of the zircon fine particles containedin the second glass layer is preferably from 0.5 to 2% by weight.

In the product having a glass layer of the third invention, it ispreferred that the base body has a larger linear thermal expansioncoefficient than the first glass layer. According to the configuration,not only the second glass layer receives compression stress from thefirst glass layer, but also the first glass layer receives compressionstress from the base body through the sintering process of the basebody, the melting process of the glazing material layers and the coolingprocess of the base body and the glass layers in the baking step,whereby not only the second glass layer but the first glass layer arecompacted. Therefore, in the product having a glass layer of the thirdinvention, cracks in the glass layer or the like are difficult to beformed.

In the product having a glass layer of the third invention, it ispreferred that the first glass layer and the second glass layer have adifference in linear thermal expansion coefficient of from 1×10⁻⁷ to1×10⁻⁶/° C. In the case where the difference in thermal expansioncoefficient between the first glass layer and the second glass layer issmaller than the range, a desired surface hardness cannot be obtained,and on the other hand, it is larger than the range, the compressionstress received by the second glass layer from the first glass layerbecomes too large to cause possibility of breakage of the second glasslayer. In particular, according to the results of experiment by theinventors, it is practical that the first glass layer and the secondglass layer have a difference in linear thermal expansion coefficient offrom 2×10⁻⁷ to 5×10⁻⁷/° C.

In this case, it is preferred that the first glass layer and the secondglass layer have a difference in thickness of from 10/1 to 30/1.According to the configuration, even in the case where the appearance ofthe second glass layer is poor due to the inclusion of the antibacterialmetal, such as Ag and the like, in the second glass layer, such asurface is obtained that has substantially no difference on appearancefrom the case where only the first glass layer is formed, and a producthaving a glass layer having an appearance of the surface that isexcellent in design can be obtained.

Depending on the composition and the thickness of the second glasslayer, interference of light on the interface with the first glass layeris difficult to be formed, and thus iridescent can also be prevented.Further, depending on the composition of the second glass layer, thesecond glass layer is formed as a crystallized vitreous material to makeit opaque.

It is preferred that the base body and the first glass layer have adifference in linear thermal expansion coefficient of from 1×10⁻⁷ to1×10⁻⁶/° C. In the case where the difference in thermal expansioncoefficient between the base body and the first glass layer is smallerthan the range, a desired strength cannot be obtained, and on the otherhand, it is larger than the range, the compression stress received bythe first glass layer from the base body becomes too large to causepossibility of breakage of the first glass layer. In particular,according to the results of experiment by the inventors, it is practicalthat the base body and the first glass layer have a difference in linearthermal expansion coefficient of from 2×10⁻⁷ to 5×10⁻⁷/° C.

According to the results of experiment by the inventors, in the producthaving a glass layer of the third invention, the second glass layercontains a larger amount of potassium and a smaller amount of sodiumthan the first glass layer. Potassium has a larger ionic radius thansodium. Therefore, it is considered that upon forming the glass layersof the product having a glass layer of the third invention, sodium ionsin the second glass layer are ion-exchanged by potassium ions in thefirst glass layer to cause a compression stress in the second glasslayer, whereby the strength of the second glass layer is increased.

The product having a glass layer of the third invention has large stainresistant effect in the case where an antibacterial metal is containedin the second glass layer. In particular, in the product having a glasslayer of the third invention, since the antibacterial metal is containedonly in the second glass layer among the glass layers, the concentrationof the antibacterial metal on the surface side can be increased evenwhen a smaller amount of the antibacterial metal than the conventionalproduct is employed, whereby higher antibacterial function can beexerted. Further, unnecessary consumption of the antibacterial metal canbe prevented.

As the antibacterial metal herein, those similar to the first and secondinventions can be employed.

Furthermore, in the product having a glass layer of the third invention,it is preferred that a water repellent layer containing a waterrepellent component is formed on the surface side of the second glasslayer. According to the configuration, even when water containing alarge amount of stain components is applied to the surface having aslight amount of flaws, the stain is difficult to remain owing to thewater repellent function to exhibit excellent stain resistant effect.

In this case, the same water repellent treatment step as in the firstand second inventions can be carried out.

In the product having a glass layer of the third invention, the basebody may be a ceramic product main body. The product of this case is aceramic product, such as a lavatory bowl, a lavatory sink and the like.These ceramic products particularly require the effect because they areoften washed with a brash by using a cleanser containing water and anabrasive.

The process for producing a product having a glass layer of the thirdinvention comprises a preparation step of preparing a base body and aglazing material capable of forming a glass layer on a surface of thebase body, a glazing step of forming a glazing material layer comprisingthe glazing material on a surface of the base body, and a baking step ofbaking the base body and the glazing material layer to obtain a productcomprising the base body and the glass layer, characterized in that theglazing material comprises a first glazing material that is formed on aside of the base body and forms a first glass layer, and a secondglazing material that is formed on an outer side and forms a secondglass layer that has a smaller linear thermal expansion coefficient thanthe first glass layer and has hard fine particles dispersed on asurface. The product having a glass layer of the third invention can beproduced by the production process of the third invention.

In the process for producing a product having a glass layer of the thirdinvention, it is possible in the glazing step that a first glazingmaterial layer comprising the first glazing material is formed, and thena second glazing material layer comprising the second glazing materialis formed on the first glazing material layer. In the product having aglass layer of the third invention thus obtained, the first glazingmaterial is impregnated into the surface side of the base body since thefirst glazing material is glazed on the base body to form a firstglazing material layer, and the first glazing material impregnated intothe base body also forms the first glass layer inside the base body.Therefore, the first glass layer is firmly adhered on the base body.Further, in the base body, because the second glazing material is glazedon the first glazing material layer to form the second glazing materiallayer, the second glazing material is impregnated into the first glazingmaterial layer, whereby the first glass layer and the second glass layerare firmly adhered, and also the formation of cracks growing at theinterface thereof can be prevented. According to the configuration, thebaking step can be completed all at once, and reduction in productioncost can be realized.

Furthermore, in the process for producing a product having a glass layerof the third invention, it is preferred that the first glazing materialcontains potassium, and the second glazing material contains sodium.Because potassium has a larger ionic radius than sodium, sodium ions inthe second glazing material are ion-exchanged by potassium ions in thefirst glazing material by using these first and second glazingmaterials. Accordingly, a product having a glass layer of the thirdinvention can be obtained that has the second glass layer containing alarger amount of potassium and a smaller amount of sodium than the firstglass layer.

In the process for producing a product having a glass layer of the thirdinvention, it is possible that the second glazing material contains anantibacterial metal. According to the configuration, a product having aglass layer imparted with antibacterial function can be produced.

Furthermore, in the process for producing a product having a glass layerof the third invention, it is possible that the second glazing materialhas a higher viscosity upon melting than the first glazing material.According to the configuration, aggregation of the hard fine particlesdispersed in the second glass layer can be prevented, and thus the hardfine particles can be present in such a state that they are suitablydispersed on the surface. Further, degasification upon baking issmoothly carried out, whereby blister of the ceramic product can beprevented, and also the rate of diffusion of the antibacterial metalfrom the second glass layer to the first glass layer upon baking isdecreased, so as to produce a product having a glass layer having theconcentration of the antibacterial metal on the surface that ismaintained at a high level.

Furthermore, the process for producing a product having a glass layer ofthe third invention may have a water repellent treatment step ofsubjecting the surface of the glass layer to a water repellenttreatment. According to the configuration, such a product having a glasslayer can be obtained that stain is difficult to remain.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a base body and a first glazingmaterial layer of Example relating to the first invention.

FIG. 2 is a cross sectional view of a base body, a first glazingmaterial layer and a second glazing material layer of Example relatingto the first invention.

FIG. 3 is a cross sectional view of a base body, a first glass layer anda second glass layer of Example relating to the first invention.

FIG. 4 is a cross sectional view of a base body, a first glass layer, asecond glass layer and a water repellent layer of Example relating tothe first invention.

FIG. 5 is a cross sectional view of a base body and a glass layer ofComparative Examples 1 and 2 relating to the first invention.

FIG. 6 is a cross sectional view of a base material and a first glazingmaterial layer of Example relating to the second invention.

FIG. 7 is a cross sectional view of a base material, a first glazingmaterial layer and a second glazing material layer of Example relatingto the second invention.

FIG. 8 is a cross sectional view of a ceramic product main body, a firstglass layer and a second glass layer of Example relating to the secondinvention.

FIG. 9 is a cross sectional view of a ceramic product main body, a firstglass layer, a second glass layer and a water repellent layer of Examplerelating to the second invention.

FIG. 10 is a cross sectional view of a ceramic product main body and aglass layer of Comparative Example relating to the second invention.

FIG. 11 is a result of a potassium surface analysis by EPMA of a crosssection of a sample of Example relating to the second invention.

FIG. 12 is a cross sectional view of a base material and a first glazingmaterial layer of Examples 1 to 7 relating to the third invention.

FIG. 13 is a cross sectional view of a base material, a first glazingmaterial layer and a second glazing material layer of Examples 1 to 7relating to the third invention.

FIG. 14 is a cross sectional view of a ceramic product main body, afirst glass layer and a second glass layer of Examples 1 to 7 relatingto the third invention.

FIG. 15 is a cross sectional view of a sample of Examples 1 to 7relating to the third invention.

FIG. 16 is an upper view of a sample of Examples 1 to 7 relating to thethird invention.

FIG. 17 is across sectional view of a sample of Comparative Examples 1and 2 relating to the third invention.

FIG. 18 is across sectional view of a sample of Comparative Examples 3and 4 relating to the third invention.

FIG. 19 is a result of a potassium surface analysis by EPMA of a crosssection of a sample of Examples 1 to 7 relating to the third invention.

BEST MODE FOR CARRYING OUT THE INVENTION

(First Invention)

Example practicing the first invention and Comparative Examples 1 and 2will be described below along with FIGS. 1 to 5.

EXAMPLE

“Preparation Step” of “Antibacterial Treatment Step”

A base material for tiles of the following composition is prepared as aceramic molded article, and the base material for tiles is cut into aquadrate of 50±2 mm square (thickness: 10 mm or less), which isdesignated as a base body 1 shown in FIG. 1 and FIG. 2. (BlendingProportions for Base Material for Tiles (% by mass)) Feldspar 28.2Silica sand 11.8 Sericite 15.0 Clay 45.0

A first glazing material and a second glazing material having thefollowing compositions are prepared. (Blending Proportions for FirstGlazing Material (% by mass)) Feldspar 35.0 Silica sand 46.9 Lime 15.9Clay 2.2

The first glazing material contains 2% by mass of K₂O. (BlendingProportions for Second Glazing Material (% by mass)) Silica sand 31.0Lime 6.0 Clay 13.0 Antibacterial agent 50.0

The antibacterial agent has the following composition (% by mass). Ag₂O25.88 P₂O₅ 4.98 CaO 0.01 SiO₂ 56.84 Al₂O₃ 9.36 Fe₂O₃ 0.10 K₂O 0.43 Na₂O0.06 SrO 0.01 Ignition loss 2.34

The second glazing material contains 2% by mass of Na₂O.

“Vitrification Step” of “Antibacterial Treatment Step”

As shown in FIG. 1, the first glazing material is glazed on the surfaceof the base body 1 to form a first glazing material layer 2, and then asshown in FIG. 2, the second glazing material is glazed on the surfaceside of the first glazing material layer 2 to form a second glazingmaterial layer 3.

The base body 1 having the first glazing material layer 2 and the secondglazing material layer 3 is baked at 1,210° C. According to theprocedure, the first glazing material layer 2 and the second glazingmaterial layer 3 are melted to form a first glass layer 4 and a secondglass layer 5 on the base body 1 as shown in FIG. 3.

Herein, since the second glazing material layer 3 has a higher viscosityupon melting than the first glazing material layer 2, most of a silvercompound 6 added to the second glazing material as an antibacterialmetal stays in the second glass layer 5. Furthermore, the first glasslayer 4 and the second glass layer 5 have a difference in thickness of20/1.

“Water Repellent Treatment Step”

Thereafter, a water repellent treatment step is carried out on thesurface of the second glass layer 5.

A first agent is prepared, which is formed with C₈F₁₇CH₂CH₂Si(OCH₃) ₃

as a perfluoroalkyl group-containing organic silicon compound and

-   -   Si (CH₃O)₃CH₂CH₂—(Si(CH₃) ₂O)₁₀—Si(CH₃)₂CH₂CH₂Si(OCH₃)₃ as a        hydrolyzable group-containing polymethylsiloxane compound, which        are co-hydrolyzed in a hydrophilic solvent containing 0.1N        aqueous hydrochloric acid, t-butanol and hexane. It is        considered that they contain silanol (Si—OH) groups        respectively.

A mixture of polyorganosiloxane (HO—(Si(CH₃)₂O)₃₀—Si(CH₃)₂OH) andmethanesulfonic acid as a strong acid is prepared as a second agent.

5 ml of the second agent is added to and mixed with 5 ml of the firstagent to form a water repellent treatment liquid. The water repellenttreatment liquid is coated on the surface of the second glass layer 5 toform a film. Thereafter, it is allowed to stand for about 10 minutes todry it. Thereafter, the surface is washed with ethanol and dried.

Through the foregoing procedures, as shown in FIG. 4, a sample isobtained, which comprises the base body 1, the first glass layer 4comprising the first glazing material formed on the base body 1, thesecond glass layer 5 comprising the second glazing material, which isdifferent from the first glazing material, containing the antibacterialmetal and formed on the outer side of the first glass layer 4, and awater repellent layer 7 containing the water repellent component formedon the surface side of the second glass layer 5.

In the sample of Example, because the first glass layer 4 and the secondglass layer 5 have a difference in thickness of 20/1, such a surface isobtained that has substantially no difference on appearance from thecase where only the first glass layer 4 is formed, and the surfacehaving an appearance that is excellent in design is obtained, eventhough the second glass layer 5 itself has poor appearance due to theinclusion of the silver compound 6.

Comparative Example 1

As shown in FIG. 5, a glazing material having the following compositionis glazed on a base material of the same kind as Example to form aglazing material layer. (Blending Proportions for Glazing Material (% bymass)) Feldspar 53.7 Silica sand 9.8 Lime 12.3 Dolomite 4.8 Gairome clay5.1 Zinc white 2.0 Zircon 10.1 Silicate frit 2.2

0.5% by mass in terms of outside account of silver powder (purity: 99%or more, average particle diameter 10 μm) is added to the blend to forma glazing material.

The base body 1 having the glazing material layer is baked at 1,210° C.According to the procedures, the glazing material layer is melted toform a glass layer 8 on the base body 1 as shown in FIG. 5. Thus, asample is obtained, which comprises the base body 1 and a glass layer 8containing the antibacterial metal and comprising the glazing material,which is formed on the base body 1.

Comparative Example 2

A glazing material having a concentration of the silver powder in theglazing material of 5.0% by mass, which is 10 times that of ComparativeExample 1, is used. The others, the process for stain resistanttreatment and the constitution of the sample, are the same asComparative Example 1.

(Evaluation)

Three pieces each of the samples of Example and Comparative Examples 1and 2 are prepared and subjected to an antibacterial performance test bythe film method. The results are shown in Table 1. TABLE 1 Esherichiacoli (IFO3972) Staphylococcus aureus (IFO12732) Nutrition ComparativeComparative Comparative Comparative concentration Example Example 1Example 2 Example Example 1 Example 2 1/500 NB 5.5 2.8 4.0 4.8 2.3 3.21/200 NB 4.2 1.4 2.5 3.7 1.1 2.1  1/50 NB 2.7 0.0 0.2 2.3 0.0 0.1

It is understood from Table 1 that with respect to the antibacterialfunction for both kinds of bacteria, an average change rate differenceof 2.0 or more is maintained even when the nutrition concentration isincreased in Example, whereas an average change rate difference of 2.0or more is maintained only in the case of {fraction (1/500)} NB or lessin Comparative Example 1 and in the case of {fraction (1/200)} NB orless in Comparative Example 2. Therefore, it is understood that Exampleis excellent in stain resistant effect in comparison to ComparativeExamples 1 and 2 even though the using amount of the silver powder inExample is smaller than those in Comparative Examples 1 and 2.

It is understood from the foregoing that because the silver compound 6is present in the second glass layer 5 on the surface side in Example,the concentration thereof on the surface becomes high with the sameamount of the silver compound 6 in comparison to the case where theantibacterial metal is dispersed over the entire glass layer 8 as inComparative Examples 1 and 2, whereby excellent antibacterial functionis exerted, and unnecessary consumption of the antibacterial metal canalso be prevented. In particular, because the phosphoric acid compoundis contained in the second glazing material in Example, theantibacterial function owing to the antibacterial metal is liable to beexerted. Further, because the water repellent layer 7 is formed on thesurface of the second glass layer 5 in Example, both the antibacterialfunction and the water repellent function are imparted, and thus evenwhen water containing such a large amount of stain components is usedthat the stain resistant effect becomes insufficient only by theantibacterial function, the stain is difficult to remain owing to thewater repellent function, so as to fully exerting the stain resistanteffect.

Therefore, it is understood that according to the process for stainresistant treatment of Example, such a product having a glass layer canbe produced that can be produced at low cost and can exhibit excellentantibacterial function.

Further, in the process for stain resistant treatment of Example,degasification upon baking can be smoothly carried out to preventblister of the sample.

(Second Invention)

Example practicing the second invention and Comparative Example will bedescribed below.

EXAMPLE

“Preparation Step”

A base material for tiles 1 is prepared from the following compositioncut into a quadrate of 50±2 mm square (thickness: 10 mm or less).(Blending Proportions for Base Material 1 (% by mass)) Feldspar 28.2Silica sand 11.8 Sericite 15.0 Clay 45.0

A first glazing material and a second glazing material having thefollowing compositions are prepared. (Blending Proportions for FirstGlazing Material (% by mass)) Feldspar 35.0 Silica sand 46.9 Lime 15.9Clay 2.2

The first glazing material contains 2% by mass of K₂O. (BlendingProportions for Second Glazing Material (% by mass)) Silica sand 31.0Lime 6.0 Clay 13.0 Antibacterial agent 50.0

The antibacterial agent has the following composition (% by mass). Ag₂O25.88 P₂O₅ 4.98 CaO 0.01 SiO₂ 56.84 Al₂O₃ 9.36 Fe₂O₃ 0.10 K₂O 0.43 Na₂O0.06 SrO 0.01 Ignition loss 2.34

The second glazing material contains 2% by mass of Na₂O.

“Glazing Step”

As shown in FIG. 6, the first glazing material is glazed on the surfaceof the base material 1 to form a first glazing material layer 2, andthen as shown in FIG. 7, the second glazing material is glazed on thesurface side of the first glazing material layer 2 to form a secondglazing material layer 3.

“Baking Step”

The base material 1 having the first glazing material layer 2 and thesecond glazing material layer 3 is baked at 1,210° C. According to theprocedure, the base material 1 is sintered, and the first glazingmaterial layer 2 and the second glazing material layer 3 are melted toform a first glass layer 4 and a second glass layer 5 on a ceramicproduct main body 1 as shown in FIG. 8.

Herein, the second glass layer 5 has a smaller linear thermal expansioncoefficient than the linear thermal expansion coefficient of the firstglass layer 4, and the difference therebetween is 3×10⁻⁷/° C. Further,the first glass layer 4 has a smaller linear thermal expansioncoefficient than the linear thermal expansion coefficient of the ceramicproduct main body 1, and the difference therebetween is 4×10⁻⁷/° C.Furthermore, the first glass layer 4 and the second glass layer 5 have adifference in thickness of 20/1. The second glass layer 5 has the silvercompound 6 as an antibacterial metal dispersed therein.

“Water Repellent Treatment Step”

The following water repellent treatment step is then carried out on thesurface of the second glass layer 5.

A first agent is prepared, which is formed with C₈F₁₇CH₂CH₂Si (OCH₃)₃

as a perfluoroalkyl group-containing organic silicon compound and

-   -   Si(CH₃O)₃CH₂CH₂—(Si(CH₃)₂O)₁₀—Si(CH₃)₂CH₂CH₂Si(OCH₃)₃ as a        hydrolyzable group-containing polymethylsiloxane compound, which        are co-hydrolyzed in a hydrophilic solvent containing 0.1N        aqueous hydrochloric acid, t-butanol and hexane. It is        considered that they contain silanol (Si—OH) groups        respectively.

A mixture of polyorganosiloxane (HO—(Si(CH₃)₂O)₃₀—Si(CH₃)₂OH) andmethanesulfonic acid as a strong acid is prepared as a second agent.

5 ml of the second agent is added to and mixed with 5 ml of the firstagent to form a water repellent treatment liquid. The water repellenttreatment liquid is coated on the surface of the ceramic product mainbody 1 having the first glass layer 4 and the second glass layer 5 andthen dried by allowing to stand for about 10 minutes. Thereafter, thesurface is washed with ethanol and dried.

Through the foregoing procedures, as shown in FIG. 9, a sample isobtained, which comprises the ceramic product main body 1, the firstglass layer 4 comprising the first glazing material formed on theceramic product main body 1, the second glass layer 5 comprising thesecond glazing material, which is different from the first glazingmaterial, containing the antibacterial metal and formed on the outerside of the first glass layer 4, and a water repellent layer 7containing the water repellent component formed on the surface side ofthe second glass layer 5.

COMPARATIVE EXAMPLE

As shown in FIG. 10, a glazing material having the following compositionis glazed on a base material 1 of the same kind as Example to form aglazing material layer. (Blending Proportions for Glazing Material (% bymass)) Feldspar 10.0 Kaolin 5.0 Silicate frit 85.0

The silicate frit herein has the following composition (% by mass). Thesilicate frit herein has the following composition (% by mass). SiO₂67.4 Al₂O₃ 8.6 MgO 2.7 CaO 5.7 SrO 3.2 Na₂O 2.3 K₂O 3.2 B₂O₃ 3.5 ZnO 2.3MoO₃ 1.1

The base material 1 having the glazing material layer is baked at 1,210°C. According to the procedures, the glazing material layer is melted toform a glass layer 8 on the ceramic product main body 1 as shown in FIG.10. Thus, a sample is obtained, which comprises the ceramic product mainbody 1 and a glass layer 8 containing the antibacterial metal andcomprising the glazing material, which is formed on the base body 1.

(Evaluation)

Samples of Example and Comparative Example are prepared and subjected tothe following brushing test.

(Brushing Test)

A commercially available toothbrush having a commercially availableabrasive coated is prepared, and the surface of the sample is scrubbedwith the toothbrush 20 times under a constant pressure. According to theprocedure, the number of flaws and the total length of the flaws (mm)per 4 cm² are obtained.

The results are shown in Table 2. TABLE 2 Number of flaws 0.7 (mm) 0.3to 0.6 0 to 0.2 Total length or more (mm) (mm) of flaws (mm) Comparative9 10 8 13.7 Example Example 1 4 2 2.8

It is understood from Table 2 that in the sample of Example, the firstglass layer 4, the second glass layer 5 and the ceramic product mainbody 1 are difficult to be damaged in comparison to the sample ofComparative Example. It is considered this is caused by the followingreasons (1) to (4).

(1) In Example, because the linear thermal expansion coefficient of thesecond glass layer is smaller than the linear thermal expansioncoefficient of the first glass layer 4, the second glass layer 5receives compression stress by contraction of the first glass layer 4through the melting process of the first and second glazing materiallayers 2 and 3 and the cooling process of the first and second glasslayers 4 and 5 in the baking step. Therefore, the second glass layer 5is compacted to have high surface hardness. Accordingly, it isunderstood that the sample of Example is difficult to suffer formationof cracks in the glass layer and the like due to flaws and is alsodifficult to suffer attachment of stain due to flaws.

(2) Because the ceramic product main body 1 has a larger linear thermalexpansion coefficient than the first glass layer 4, the first glasslayer 4 receives compression stress from the ceramic product main body1, and the first glass layer 4 is compacted. Therefore, the sample ofExample is difficult to suffer growth of cracks formed in the glasslayer and the like.

(3) Furthermore, it is understood that as shown in FIG. 11, the X-raystrength of the potassium Kα line in Example is in a low range of from198 to 331 cps in the first glass layer 4 but is in a high range of from331 to 463 cps in the second glass layer 5. Therefore, in Example, itcan be said that sodium ions having a small ionic radius present in thesecond glass layer 5 are ion-exchanged by potassium ions having a largeionic radius present in the first glass layer 4, and potassium ions arediffused in the second glass layer 5. The second glass layer 5 thusforms compression stress by itself, and the second glass layer 5 isreinforced.

(4) Because the first glazing material is glazed on the base material 1to form the first glazing material layer 2 in the sample of Example, thefirst glazing material is impregnated into the surface side of the basematerial 1, and the first glazing material impregnated into the basematerial 1 also constitutes the first glass layer 4 inside the ceramicproduct main body 1 comprising the base material 1. Therefore, the firstglass layer 4 is firmly adhered to the ceramic product main body 1. Thesecond glazing material 3 is glazed on the first glazing material layer2 to form the second glazing material layer 3 in this sample, the secondglazing material is impregnated into the first glazing material layer 2,whereby the first glass layer 4 and the second glass layer 5 are firmlyadhered, and the formation of cracks growing at the interfacetherebetween can also be prevented. Further, according to theconfiguration, the baking step can be completed all at once to realizereduction in production cost.

Further, because the first glass layer 4 and the second glass layer 5have a difference in thickness of 20/1, such a surface is obtained thathas substantially no difference on appearance from the case where onlythe first glass layer 4 is formed even though the second glass layer 5itself has poor appearance due to the inclusion of the silver compound6.

Furthermore, in the samples of Example and Comparative Example, becausethe second glass layer 5 or the glass layer 8 contains the silvercompound 6 as an antibacterial metal, they have antibacterial function.In Example, because only the second glass layer 5 among the glass layerscontains the silver compound 6, the concentration of the silver compound6 on the surface side can be increased even when a smaller amount of thesilver compound than Comparative Example is used, so as to realizeexertion of higher antibacterial function. Unnecessary consumption ofthe silver compound 6 can also be prevented. In Example, because thesecond glazing material has a higher viscosity upon melting than thefirst glazing material, degasification upon baking is smoothly carriedout, whereby blister of the sample can be prevented, and also the rateof diffusion of the silver compound 6 from the second glass layer 5 tothe first glass layer 4 upon baking is decreased, so as to produce asample having the concentration of the silver compound 6 on the surfacethat is maintained at a high level.

In the sample of Example, because the water repellent layer 7 is formedon the surface of the second glass layer 5, even when water containing alarge amount of stain components is applied to the surface of the secondglass layer 5 having a slight amount of flaws, the stain is difficult toremain owing to the water repellent function thereof to exert excellentstain resistant effect. Particularly, in Example, because the phosphoricacid compound is contained in the second glazing material, theantibacterial function due to the silver compound 6 is liable to beexerted. In Example, because the water repellent layer 7 is formed onthe surface of the second glass layer 5, both the antibacterial functionand the water repellent function are imparted, and thus in the casewhere water containing a large amount of stain components, to which thestain resistant effect is insufficient only by the antibacterialfunction, is applied, the stain is difficult to remain owing to thewater repellent function, whereby the stain resistant effect issufficiently exerted.

(Third Invention)

Examples 1 to 7 practicing the third invention and Comparative Examples1 to 4 will be described below.

Example 1

“Preparation Step” As shown in FIG. 12 and FIG. 13, a base material fortiles 1 is prepared from the following composition cut into a quadrateof 50±2 mm square (thickness: 10 mm or less). (Blending Proportions forBase Material 1 (% by mass)) Feldspar 28.2 Silica sand 11.8 Sericite15.0 Clay 45.0

A first glazing material and a second glazing material having thefollowing compositions are prepared. (Blending Proportions for FirstGlazing Material (% by mass)) Feldspar 42.456 Frit 1.617 Lime 11.827Dolomite 5.054 Zinc white 1.516 Gairome clay 4.043 Alumina 1.769 Silicasand 9.603 Opacifier 6.368 Chamotte fireproof material 15.163 Pigment0.581

The frit herein has the following composition (% by mass). The fritherein has the following composition (% by mass). SiO₂ 49.3 Al₂O₃ 11.1CaO 0.2 Na₂O 19.1 K₂O 1.0 B₂O₃ 19.2

The first glazing material contains 2% by mass of K₂O. (BlendingProportions for Second Glazing Material (% by mass)) Silica sand 31.0Lime 6.0 Clay 13.0 Antibacterial agent 50.0

The antibacterial agent has the following composition (% by mass). Theantibacterial agent has the following composition (% by mass). Ag₂O25.88 P₂O₅ 4.98 CaO 0.01 SiO₂ 56.84 Al₂O₃ 9.36 Fe₂O₃ 0.10 K₂O 0.43 Na₂O0.06 SrO 0.01 Ignition loss 2.34

1% by mass in terms of outside account of zircon fine particles 3 ahaving an average particle diameter of 0.81 μm are contained as hardfine particle in the foregoing composition to form the second glazingmaterial. The second glazing material contains 2% by mass of Na₂O.

“Glazing Step”

As shown in FIG. 12, the first glazing material is glazed on the surfaceof the base material 1 to form a first glazing material layer 2, andthen as shown in FIG. 13, the second glazing material is glazed on thesurface side of the first glazing material layer 2 to form a secondglazing material layer 3.

“Baking Step”

The base material 1 having the first glazing material layer 2 and thesecond glazing material layer 3 is baked at 1,210° C. According to theprocedure, the base material 1 is sintered, and the first glazingmaterial layer 2 and the second glazing material layer 3 are melted toform a first glass layer 4 and a second glass layer 5 on a ceramicproduct main body 1 as shown in FIG. 14. The zircon fine particles 3 aare present in the surface of the second glass layer 5 in a dispersedstate.

Herein, the second glass layer 5 has a smaller linear thermal expansioncoefficient than the linear thermal expansion coefficient of the firstglass layer 4, and the difference therebetween is 3×10⁻⁷/° C. Further,the first glass layer 4 has a smaller linear thermal expansioncoefficient than the linear thermal expansion coefficient of the ceramicproduct main body 1, and the difference therebetween is 4×10⁻⁷/° C.Furthermore, the first glass layer 4 and the second glass layer 5 have adifference in thickness of 20/1. The second glass layer 5 has the silvercompound 6 as an antibacterial metal dispersed therein.

“Water Repellent Treatment Step”

The following water repellent treatment step is then carried out on thesurface of the second glass layer 5.

A first agent is prepared, which is formed with C₈F₁₇CH₂CH₂Si (OCH₃)₃

as a perfluoroalkyl group-containing organic silicon compound andSi(CH₃O)₃CH₂CH₂—(Si(CH₃) ₂O)₁₀—Si(CH₃)₂CH₂CH₂Si(OCH₃)₃ as a hydrolyzablegroup-containing polymethylsiloxane compound, which are co-hydrolyzed ina hydrophilic solvent containing 0.1N aqueous hydrochloric acid,t-butanol and hexane. It is considered that they contain silanol (Si—OH)groups respectively.

A mixture of polyorganosiloxane (HO—(Si(CH₃)₂O)₃₀—Si(CH₃)₂OH) andmethanesulfonic acid as a strong acid is prepared as a second agent.

5 ml of the second agent is added to and mixed with 5 ml of the firstagent to form a water repellent treatment liquid. The water repellenttreatment liquid is coated on the surface of the ceramic product mainbody 1 having the first glass layer 4 and the second glass layer 5 andthen dried by allowing to stand for about 10 minutes. Thereafter, thesurface is washed with ethanol and dried.

Through the foregoing procedures, as shown in FIG. 15 and FIG. 16, asample is obtained, which comprises the ceramic product main body 1, thefirst glass layer 4 comprising the first glazing material formed on theceramic product main body 1, the second glass layer 5 comprising thesecond glazing material, which is different from the first glazingmaterial, containing the antibacterial metal and formed on the outerside of the first glass layer 4, and a water repellent layer 7containing the water repellent component formed on the surface side ofthe second glass layer 5, and further contains the zircon fine particle3 a present over the second glass layer and the surface of the waterrepellent layer 7.

Example 2

In the preparation step of Example 1, 2% by mass in terms of outsideaccount of the zircon fine particles 3 a in Example 1 are contained inthe second glazing material. The other conditions are the same as inExample 1.

Example 3

In the preparation step of Example 1, 1% by mass in terms of outsideaccount of zircon fine particles 3 a having an average particle diameterof 1.55 μm are contained as hard fine particle in the second glazingmaterial. The other conditions are the same as in Example 1.

Example 4

In the preparation step of Example 1, 2% by mass in terms of outsideaccount of the zircon fine particles 3 a in Example 3 are contained inthe second glazing material. The other conditions are the same as inExample 1.

Example 5

In the preparation step of Example 1, 1% by mass in terms of outsideaccount of zircon fine particles 3 a having an average particle diameterof 20 μm are contained as hard fine particle in the second glazingmaterial. The other conditions are the same as in Example 1.

Example 6

In the preparation step of Example 1, 2% by mass in terms of outsideaccount of the zircon fine particles 3 a in Example 5 are contained inthe second glazing material. The other conditions are the same as inExample 1.

Example 7

In the preparation step of Example 1, 4% by mass in terms of outsideaccount of the zircon fine particles 3 a in Example 5 are contained inthe second glazing material. The other conditions are the same as inExample 1.

Comparative Example 1

As shown in FIG. 17, a glazing material having the following compositionis glazed on a base material 1 of the same kind as Example 1 to form aglazing material layer. (Blending Proportions for Glazing Material (% bymass)) Feldspar 10.0 Kaolin 5.0 Frit 85.0

The frit herein has the following composition (% by mass) The fritherein has the following composition (% by mass). SiO₂ 67.4 Al₂O₃ 8.6MgO 2.7 CaO 5.7 SrO 3.2 Na₂O 2.3 K₂O 3.2 B₂O₃ 3.5 ZnO 2.3 MoO₃ 1.1

The base material 1 having the glazing material layer is baked at 1,210°C. According to the procedures, the glazing material layer is melted toform a glass layer 8 on the ceramic product main body 1. Thus, a sampleis obtained, which comprises the ceramic product main body 1 and a glasslayer 8 comprising the glazing material formed on the base body 1.

Comparative Example 2

A glazing material having the following composition is glazed on a basematerial 1 of the same kind as Example 1 to form a glazing materiallayer. The base material 1 having the glazing material layer is baked at1,210° C. to obtain the similar sample as the sample of ComparativeExample 1 shown in FIG. 17. (Blending Proportions for Glazing Material(% by mass)) Feldspar 42.456 Frit 1.617 Lime 11.827 Dolomite 5.054 Zincwhite 1.516 Gairome clay 4.043 Alumina 1.769 Silica sand 9.603 Opacifier6.368 Chamotte fireproof material 15.163 Pigment 0.581

The frit herein is the same as in Example 1. 6.3% by mass in terms ofoutside account of zircon fine particles having an average particlediameter of 1.55 μm are contained in the foregoing composition to form aglazing material.

Comparative Example 3

The same base material 1 as in Example 1, a first glazing materialcomprising the glazing material of Comparative Example 2, and a secondglazing material having the following composition are prepared. A basematerial 1 having a first glazing material layer and a second glazingmaterial layer is baked at 1,210° C. to obtain a sample. According tothe procedures, as shown in FIG. 18, a ceramic product main body 1, afirst glass layer 9 comprising the first glazing material formed on theceramic product main body 1, and a second glass layer 10 comprising thesecond glazing material formed on the glass layer 9. (BlendingProportions for Second Glazing Material (% by mass)) Silica sand 31.0Lime 2.3 Clay 12.4 Zinc white 3.9 Frit 0.5 Antibacterial agent 50.0

The frit is the same as in Comparative Example 1, and the antibacterialagent is the same as in Example 1.

Comparative Example 4

The same base material 1 as in Example 1, a first glazing materialcomprising the glazing material of Comparative Example 2, and a secondglazing material having the following composition are prepared. A basematerial 1 having a first glazing material layer and a second glazingmaterial layer is baked at 1,210° C. to obtain a sample that is similarto the sample of Comparative Example 3 shown in FIG. 18. (BlendingProportions for Second Glazing Material (% by mass)) Silica sand 33.0Lime 8.5 Alumina 7.0 Antibacterial agent 51.2

The antibacterial agent is the same as in Example 1.

(Evaluation)

Samples of Examples 1 to 7 and Comparative Examples 1 to 4 are prepared,and pinholes on the surface are confirmed with a digital microscope toevaluate the smoothness. They are shown in Table 3. In Table 3, thoseexcellent in smoothness are shown with A, and those lacking smoothnessare shown with B. TABLE 3 Number of flaws 0.7 (mm) 0.3 to 0.6 0 to 0.2Total Sample Smoothness or more (mm) (mm) length of flaws (mm) Example 1A 1 1 2 1.7 2 A 0 0 0 0.0 3 A 0 1 2 0.6 4 A 1 1 4 1.8 5 A 2 2 0 3.0 6 A0 1 1 0.7 7 A 0 0 0 0.0 Comparative 1 B 9 10 8 13.7 Example 2 B 0 1 10.6 3 A 6 5 17 10.3 4 A 1 4 2 2.8

It is understood from Table 3 that the samples of Examples 1 to 7Comparative Examples 3 and 4 have substantially no pinhole on thesurface and exhibit excellent smoothness. On the other hand, the samplesof Comparative Examples 1 and 2 have pinholes on the surface even in asmall amount and are rather inferior in smoothness. This is because theglass layers of the samples of Examples 1 to 7 and Comparative Examples3 and 4 each has the first glass layer and the second glass layer, andthus even when pinholes are formed up to the first glass layer due toinfluence of the base material 1, the influence of the base material 1is difficult to extend to the second glass layer, and pinholes aredifficult to occur on the surface of the second glass layer. Therefore,it is understood that the samples of Examples 1 to 7 and ComparativeExamples 3 and 4 have higher smoothness and realize excellent stainresistance.

In the samples of Examples 1 to 7, the zircon fine particles 3 a arecontained in such an extent of amount that does not influence thecoloration of the second glass layer 5 and are dispersed in such adispersed state that does not influence the smoothness on the surface ofthe second glass layer 5, whereby excellent appearance is exerted.

Furthermore, because the samples of Examples 1 to 7 have the waterrepellent layer 7 on the surface side of the second glass layer 5, evenwhen water containing a large amount of stain components is applied tothe surface of the second glass layer 5 having a slight amount of flaws,the stain is difficult to remain owing to the water repellent functionthereof to exert excellent stain resistant effect. Moreover, in thesamples of Examples 1 to 7, because the silver compound 6 as anantibacterial metal is contained in the second glass layer 5, it hasantibacterial function, and excellent stain resistant function is alsoexerted thereby.

Samples of Examples 1 to 7 and Comparative Examples 1 to 4 are subjectedto the following brushing test.

(Brushing Test)

A commercially available toothbrush having a commercially availableabrasive coated is prepared, and the surface of the sample is scrubbedwith the toothbrush 20 times under a constant pressure. According to theprocedure, the number of flaws and the total length of the flaws (mm)per 4 cm² are obtained. The results are also shown in Table 3.

It is understood from Table 3 that the samples of Examples 1 to 7 andComparative Examples 2 and 4 are difficult to suffer formation of flaws.This is because the linear thermal expansion coefficient of the secondglass layer is smaller than the linear thermal expansion coefficient ofthe first glass layer in samples of Examples 1 to 7 and ComparativeExamples 4, and therefore the second glass layer is compacted byreceiving compression stress caused by contraction of the first glasslayer to make a high surface hardness. Particularly, in the samples ofExamples 1 to 7, large flaws are not formed since abrasion of anabrasive is inhibited by the zircon fine particles 3 a present on thewater repellent layer 7. Therefore, it is understood that in the samplesof Examples 1 to 7, stain due to flaws and cracks is difficult to beattached to exert excellent stain resistance.

Furthermore, it is understood that as shown in FIG. 19, the X-raystrength of the potassium Kα line in the samples of Examples 1 to 7 isin a low range of from 198 to 331 cps in the first glass layer 4 but isin a high range of from 331 to 463 cps in the second glass layer 5.Therefore, in the samples of Examples 1 to 7, it can be said that sodiumions having a small ionic radius present in the second glass layer 5 areion-exchanged by potassium ions having a large ionic radius present inthe first glass layer 4, and potassium ions are diffused in the secondglass layer 5. The second glass layer 5 thus forms compression stress byitself, and the second glass layer 5 is reinforced.

(Antibacterial Test)

Three pieces each of the samples of Examples 1 to 7 and ComparativeExamples 1 to 4 are prepared and subjected to an antibacterialperformance test by the film method. The average change rate differencesof Esherichia coli (IF03972) at respective nutrition concentrations areshown in Table 4. The average change rate differences of Staphylococcusaureus (IF012732) at respective nutrition concentrations are shown inTable 5. In Tables 4 and 5, no antibacterial effect is observed at anaverage change rate difference of less than 2.0. TABLE 4 ComparativeNutrition Example Example concentration 1 2 3 4 5 6 7 1 2 3 4 1/500 NB5.5 5.5 5.5 5.5 5.5 5.5 5.5 2.4 2.4 5.5 5.5 1/200 NB 4.2 4.2 4.2 4.2 4.24.2 4.2 1.2 1.2 4.2 4.2  1/50 NB 2.7 2.7 2.7 2.7 2.7 2.7 2.7 0.0 0.0 2.72.7

TABLE 5 Comparative Nutrition Example Example concentration 1 2 3 4 5 67 1 2 3 4 1/500 NB 4.8 4.8 4.8 4.8 4.8 4.8 4.8 2.2 2.2 4.8 4.8 1/200 NB3.7 3.7 3.7 3.7 3.7 3.7 3.7 0.0 0.0 3.7 3.7  1/50 NB 2.3 2.3 2.3 2.3 2.32.3 2.3 0.0 0.0 2.3 2.3

It is understood from Table 4 and Table 5 that with respect to theantibacterial function for both kinds of bacteria, an average changerate difference of 2.0 or more is maintained even when the nutritionconcentration is increased in samples of Examples 1 to 7, whereas anaverage change rate difference of 2.0 or more is maintained only in thecase of {fraction (1/500)} NB or less in samples of Comparative Examples1 and 2. Therefore, it is understood that the samples of Examples 1 to 7exert excellent in stain resistance in comparison to the samples ofComparative Examples 1 and 2. It is also understood that because thesilver compound 6 as an antibacterial metal is contained only in thesecond glass layer 5 among the glass layers in the samples of Examples 1to 7, the concentration of the silver compound 6 on the surface side canbe increased even when a smaller amount of the antibacterial agent thanthe conventional one is used, whereby exertion of higher antibacterialfunction can be realized. It is further understood that unnecessaryconsumption of the antibacterial agent can be prevented in the samplesof Examples 1 to 7.

It is understood that the samples of Examples 1 to 7 show average changerate differences of the similar level as the samples of ComparativeExamples 3 and 4. Therefore, it is understood that as shown in FIG. 15the samples of Examples 1 to 7 can exert stain resistance that isequivalent to the samples of Comparative Examples 3 and 4 even thoughthey have the zircon fine particles 3 a present over the second glasslayer 5 to the surface of the water repellent layer 7.

Therefore, the samples of Examples 1 to 7 are excellent in surfacesmoothness and are difficult to suffer formation of flaws on thesurface, and thus excellent stain resistance is certainly exerted.

Examples and Comparative Examples shown in the foregoing are onlyexemplification, and the first to third inventions may be carried out inembodiments, to which various changes are made unless they deviate fromthe substance thereof.

APPLICABILITY IN INDISTRIES

According to the process for stain resistant treatment of the firstinvention, a product having a glass layer can be produced that can beproduced at a low cost and can exhibit excellent antibacterial function.

In the reinforced ceramic product of the second invention, the surfaceof the glass layer is difficult to suffer formation of flaws.

In the product having a glass layer of the third invention, the surfaceis difficult to suffer formation of flaws, and thus excellent stainresistance is certainly exerted.

1. A process for stain resistant treatment comprising an antibacterialtreatment step of imparting antibacterial function to a surface of aceramic molded article, characterized in that said antibacterialtreatment step comprises a preparation step of preparing said ceramicmolded article, a first glazing material capable of forming a firstglass layer on a surface of the ceramic molded article, and a secondglazing material capable of forming a second glass layer containing anantibacterial metal on said surface of said ceramic molded article, anda vitrification step of forming a first glazing material layercomprising said first glazing material on a surface of said ceramicmolded article and, on a yet surface side, a second glazing materiallayer comprising said second glazing material, and melting said firstglazing material layer and said second glazing material layer to formsaid first glass layer and said second glass layer, and said secondglazing material layer has a higher viscosity upon melting than saidfirst glazing material layer.
 2. A process for stain resistant treatmentas described in claim 1, characterized in that said second glazingmaterial contains a phosphoric acid compound.
 3. A process for stainresistant treatment as described in claim 1 or 2, characterized byhaving a water repellent treatment step of subjecting a surface of saidsecond glass layer to a water repellent treatment after saidantibacterial treatment step.
 4. (Cancelled)
 5. (Cancelled) 6.(Cancelled)
 7. (Cancelled)
 8. (Cancelled)
 9. (Cancelled)
 10. A producthaving a glass layer comprising a ceramic molded article having a glasslayer, said glass layer comprising a first glass layer comprising afirst glazing material and a second glass layer formed on a yet outerside of said first glass layer and comprising a second glazing materialcontaining an antibacterial metal and a phosphoric acid compound beingdifferent from said first glazing material.
 11. A product having a glasslayer as described in claim 10, characterized in that said first glasslayer and said second glass layer have a difference in thickness of from10/1 to 30/1.
 12. (Cancelled)
 13. A product having a glass layer asdescribed in claim 10 or 11, characterized in that said second glasslayer contains a larger amount of potassium and a smaller amount ofsodium than said first glass layer.
 14. A product having a glass layeras described in claim 10 or 11, characterized in that a water repellentlayer containing a water repellent component is formed on a surface sideof said second glass layer.
 15. A reinforced ceramic product comprisinga ceramic product main body and a glass layer formed on a surface ofsaid ceramic product main body, characterized in that said glass layercomprises a first glass layer comprising a first glazing material and asecond glass layer comprising a second glazing material that is formedon an outer side of said first glass layer, contains an antibacterialmetal, and has a smaller linear thermal expansion coefficient than saidfirst glass layer.
 16. A reinforced ceramic product as described inclaim 15, characterized in that said ceramic product main body has alarger linear thermal expansion coefficient than said first glass layer.17. A reinforced ceramic product as described in claim 15 or 16,characterized in that said first glass layer and said second glass layerhave a difference in linear thermal expansion coefficient of from 1×10⁻⁷to 1×10⁻⁶/° C.
 18. A reinforced ceramic product as described in claim17, characterized in that said first glass layer and said second glasslayer have a difference in linear thermal expansion coefficient of from2×10⁻⁷ to 5×10⁻⁷/° C.
 19. A reinforced ceramic product as described inclaim 17, characterized in that said first glass layer and said secondglass layer have a difference in thickness of from 10/1 to 30/1.
 20. Areinforced ceramic product as described in claim 16, characterized inthat said ceramic product main body and said first glass layer have adifference in linear thermal expansion coefficient of from 1×10⁻⁷ to1×10⁻⁶/° C.
 21. A reinforced ceramic product as described in claim 20,characterized in that said ceramic product main body and said firstglass layer have a difference in linear thermal expansion coefficient offrom 2×10⁻⁷ to 5×10⁻⁷/° C.
 22. A reinforced ceramic product as describedin claim 15 or 16, characterized in that said second glass layercontains a larger amount of potassium and a smaller amount of sodiumthan said first glass layer.
 23. (Cancelled)
 24. A reinforced ceramicproduct as described in claim 15 or 16, characterized in that a waterrepellent layer containing a water repellent component is formed on asurface side of said second glass layer.
 25. A process for producing areinforced ceramic product comprising a preparation step of preparing abase material capable of forming a ceramic product main body and aglazing material capable of forming a glass layer on a surface of saidceramic product main body, a glazing step of forming a glazing materiallayer comprising said glazing material on a surface of said basematerial, and a baking step of baking said base material and saidglazing material layer to obtain a ceramic product comprising saidceramic product main body and said glass layer, characterized in thatsaid glazing material comprises a first glazing material that is formedon a side of the base material and forms a first glass layer, and asecond glazing material that is formed on an outer side, contains anantibacterial metal, and forms a second glass layer having a smallerlinear thermal expansion coefficient than said first glass layer.
 26. Aprocess for producing are in forced ceramic product as described inclaim 25, characterized in that, in said glazing step, a first glazingmaterial layer comprising said first glazing material is formed, andthen a second glazing material layer comprising said second glazingmaterial is formed on said first glazing material layer.
 27. A processfor producing a reinforced ceramic product as described in claim 25 or26, characterized in that said first glazing material containspotassium, and said second glazing material contains sodium. 28.(Cancelled)
 29. A process for producing a reinforced ceramic product asdescribed in claim 25 or 26, characterized in that said second glazingmaterial has a higher viscosity upon melting than said first glazingmaterial.
 30. A process for producing a reinforced ceramic product asdescribed in claim 25 or 26, characterized by having a water repellenttreatment step of subjecting a surface of said glass layer to a waterrepellent treatment.
 31. A product having a glass layer comprising aceramic product main body and a glass layer formed on a surface of saidceramic product main body, characterized in that said glass layercomprises a first glass layer comprising a first glazing material and asecond glass layer comprising a second glazing material that is formedon an outer side of said first glass layer, contains an antibacterialmetal, and has a smaller linear thermal expansion coefficient than saidfirst glass layer, and hard fine particles for preventing growth ofcracks are dispersed on a surface of said second glass layer.
 32. Aproduct having a glass layer as described in claim 31, characterized inthat said hard fine particles are zircon fine particles.
 33. A producthaving a glass layer as described in claim 31 or 32, characterized inthat said ceramic material main body has a larger linear thermalexpansion coefficient than said first glass layer.
 34. A product havinga glass layer as described in claim 31 or 32, characterized in that saidfirst glass layer and said second glass layer have a difference inlinear thermal expansion coefficient of from 1×10⁻⁷ to 1×10⁻⁶/° C.
 35. Aproduct having a glass layer as described in claim 34, characterized inthat said first glass layer and said second glass layer have adifference in linear thermal expansion coefficient of from 2×10⁻⁷ to5×10⁻⁷/° C.
 36. A product having a glass layer as described in claim 31or 32, characterized in that said first glass layer and said secondglass layer have a difference in thickness of from 10/1 to 30/1.
 37. Aproduct having a glass layer as described in claim 33, characterized inthat said ceramic product main body and said first glass layer have adifference in linear thermal expansion coefficient of from 1×10^(−l to)1×10⁻⁶/° C.
 38. A product having a glass layer as described in claim 37,characterized in that said ceramic product main body and said firstglass layer have a difference in linear thermal expansion coefficient offrom 2×10⁻⁷ to 5×10⁻⁷/° C.
 39. A product having a glass layer asdescribed in claim 31 or 32, characterized in that said second glasslayer contains a larger amount of potassium and a smaller amount ofsodium than said first glass layer.
 40. (Cancelled)
 41. A product havinga glass layer as described in claim 31 or 32, characterized in that awater repellent layer containing a water repellent component is formedon a surface side of said second glass layer.
 42. (Cancelled)
 43. Aprocess for producing a product having a glass layer comprising apreparation step of preparing a ceramic product main body and a glazingmaterial capable of forming a glass layer on a surface of the ceramicproduct main body, a glazing step of forming a glazing material layercomprising said glazing material on a surface of said ceramic productmain body, and a baking step of baking said ceramic product main bodyand said glazing material layer to obtain a product comprising saidceramic product main body and said glass layer, characterized in thatsaid glazing material comprises a first glazing material that is formedon a side of said ceramic product main body and forms a first glasslayer, and a second glazing material that is formed on an outer side,contains an antibacterial metal, and forms a second glass layer that hasa smaller linear thermal expansion coefficient than said first glasslayer and has hard fine particles for preventing growth of cracksdispersed on a surface.
 44. A process for producing a product having aglass layer as described in claim 43, characterized in that, in saidglazing step, a first glazing material layer comprising said firstglazing material is formed, and then a second glazing material layercomprising said second glazing material is formed on said first glazingmaterial layer.
 45. A process for producing a product having a glasslayer as described in claim 43 or 44, characterized in that said firstglazing material contains potassium, and said second glazing materialcontains sodium.
 46. (Cancelled)
 47. A process for producing a producthaving a glass layer as described in claim 46, characterized in thatsaid second glazing material has a higher viscosity upon melting thansaid first glazing material.
 48. A process for producing a producthaving a glass layer as described in claim 43 or 44, characterized byhaving a water repellent treatment step of subjecting a surface of saidglass layer to a water repellent treatment.